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.\" Text fragments inspired by Martin Schulze <joey@infodrom.org>.
.\"
.TH ASPRINTF 3 2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
asprintf, vasprintf \- print to allocated string
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.B #include <stdio.h>
.PP
.BI "int asprintf(char **restrict " strp ", const char *restrict " fmt ", ...);"
.BI "int vasprintf(char **restrict " strp ", const char *restrict " fmt ,
.BI "              va_list " ap );
.fi
.SH DESCRIPTION
The functions
.BR asprintf ()
and
.BR vasprintf ()
are analogs of
.BR sprintf (3)
and
.BR vsprintf (3),
except that they allocate a string large enough to hold the output
including the terminating null byte (\(aq\e0\(aq),
and return a pointer to it via the first argument.
This pointer should be passed to
.BR free (3)
to release the allocated storage when it is no longer needed.
.SH RETURN VALUE
When successful, these functions return the number of bytes printed,
just like
.BR sprintf (3).
If memory allocation wasn't possible, or some other error occurs,
these functions will return \-1, and the contents of
.I strp
are undefined.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR asprintf (),
.BR vasprintf ()
T}	Thread safety	MT-Safe locale
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
These functions are GNU extensions, not in C or POSIX.
They are also available under *BSD.
The FreeBSD implementation sets
.I strp
to NULL on error.
.SH SEE ALSO
.BR free (3),
.BR malloc (3),
.BR printf (3)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
